Cellular communications systems typically include multiple base stations for communicating with mobile stations in various geographical transmission areas. Each base station provides an interface between the mobile station and a telecommunications network. Mobile telephone systems are in use or being developed in which the geographic coverage area of the system is divided into smaller separate cells, each of which communicates with the network via a fixed station located in the cell. Mobile telephones belonging to the system are free to travel from one cell to another. When a subscriber within the same system or within an external system wishes to call a mobile subscriber within this system, the network must have information on the actual location of the mobile telephone.
Recently, the price of cellular telephones has been greatly reduced and become affordable to more people. It is common that a person owns more than one cellular phone. Some people even replace their cellular telephones as often as they replace their clothes or hairstyle. The cellular manufacturers have to release new models with different appearances, functions, and styles more frequently so as to attract the attention of buyers and occupy a favorable market share. Furthermore, the conventional projector employs a white light lamp as a light source; therefore, at least two reflector lenses and at least three light-split lenses are required to split the white light into three colors (red, green, and blue). The optical lens set is expensive. The mechanism of the optical system is complicated and the size is difficult to reduce. Further, the lamp source will generate heat at a high temperature. Another type of projector is called a digital light projector. U.S. Pat. Nos. 6,733,137 and 6,988,808 disclose such projectors. The type of projector employs DMD (digital micro-mirror device) and a color wheel for projecting. The digital mirror device has several hundreds of thousands of mirror elements and is capable of reducing a difference in chromaticness (tint) caused by performance or characteristic variation between filters or between light sources. A driving unit controls an inclination of each of the mirror elements of a DMD panel according to a corrected video signal and a revolution state of a color filter wheel. The correcting unit corrects a luminance signal for each color of the video signals by calculating a relative intensity of light having passed through each filter making up the color filter wheel using the output of a photosensor occurring when each mirror element of the DMD panel is put in the OFF state. The color filter wheel is driven by a motor and its size is not small; consequently, it is difficult to embed the projecting device into a portable device. Further, the conventional technology employs white light as the light source and it operates at high temperatures. The projector needs a lot of lenses to cooperate with the light source and the color filter wheel as well. A low-frequency flashing effect occurs due to the white light passing through the high speed revolution color wheel which is driven by the motor. As recognized herein, for portability, it is desirable to configure the projector to be as slim as possible. But the goal of size reduction is frustrated by the presence of the elements mentioned above.